The present invention relates to methods for treating Hashimoto""s thyroiditis. In particular the present invention relates to methods for treating Hashimoto""s thyroiditis by administration of a neurotoxin to a patient.
Hashimoto""s thyroiditis is a chronic condition and is the most common thyroid disorder, occurring in up to 2% of women and 0.2% of men, with the incidence increasing with age. Typical symptoms of Hashimoto""s thyroiditis are hypothyroidism, goiter and thyroid follicular hyperplasia. Patients with Hashimoto""s thyroiditis frequently develop primary hypothyroidism as a result of the chronic autoimmune destruction of the thyroid and the presence of thyroid stimulating hormone (TSH) receptor blocking antibodies.
Thyroid Function
The thyroid is an endocrine gland comprised of follicle cells and non-follicular or C cells. The follicle cells are capable of making two hormones, triiodothyronine (T3), which contains three iodine atoms and thyroxine (T4) which contains four. The action of thyroid hormone is concerned principally with the regulation of metabolic rate by, for example, increasing energy production and oxygen consumption by most normal tissues. Synthesis and release of T3 and T4 by thyroid cells in influenced by thyroid stimulating hormone (TSH, also called thyrotrophin) made by the pituitary. The C cells can make calcitonin which appears to influence calcium metabolism. Significantly, calcitonin is a potent hypocalcemic agent. Disorders of the thyroid include autoimmune disorders (such as Graves"" disease), thyroiditis (inflammation or infection of the thyroid), and cancer, all of which conditions can result in hypothyroidism (as can occur in Hashimoto""s thyroiditis) or hyperthyroidism (thyroidtoxicosis, as can occur in Graves"" disease). An enlarged thyroid (goiter) can by euthyroid, or a symptom of either hyperthyroidism (thyroidtoxicosis) or hypothyroidism.
The normal thyroid gland weighs about fifteen grams. It is convex anteriorly and concave posteriorly as a result of its relation to the anterolateral portions of the trachea and larynx, to which it is firmly fixed by fibrous tissue. The two lateral lobes of the thyroid extend along the sides of the larynx, reaching the level of the middle of the thyroid cartilage. Each thyroid lobe resides in a bed between the trachea and larynx medially and the carotid sheath and sternocleidomastoid muscles laterally.
The thyroid is composed of an aggregation of spherical or ovate cystlike follicles of variable size. The interfollicular areas are occupied by a highly vascularized network which includes parafollicular cells (C cells) which are responsible for the secretion of calcitonin. Parathyroid hormone (PTH, made by the parathyroid glands), calcitonin (made by the C cells of the thyroid) and dihydroxycholecalciferol (metabolized from vitamin D in the kidney) are the principal hormones concerned with the metabolism of ions such as calcium, phosphate, pyrophosphate, citrate and magnesium, and with the regulation of the metabolism of bone and its organic constituents. In humans, it is believed that calcitonin acts, in a manner antagonistic to PTH, to lower plasma calcium.
The thyroid gland is enveloped by a thickened fibrous capsule. The deep cervical fascia divides into an anterior and a posterior sheath, creating a loosely applied false capsule for the thyroid. Anterior to the thyroid lobes are the strap muscles. Situated on the posterior surface of the lateral lobes of the thyroid gland are the parathyroid glands and the recurrent laryngeal nerves; the latter usually lie in a cleft between the trachea and the esophagus. The lateral lobes of the thyroid are joined by the isthmus that crosses the trachea. A pyramidal lobe is often present. The pyramidal lobe is a long, narrow projection of thyroid tissue extending upward from the isthmus lying on the surface of the thyroid cartilage. It represents a vestige of the embryonic thyroglossal duct.
Thyroid Vascular Supply
The thyroid has an abundant blood supply. Its four major arteries are the paired superior thyroid arteries, which arise from the external carotid arteries and descend several centimeters in the neck to reach the upper poles of each thyroid lobe, where they branch, and the paired inferior thyroid arteries, each of which arises from the thyrocervical trunk of the subclavian artery, runs medially behind the carotid artery and enters the lower or midpart of the thyroid lobe from behind. A fifth artery, the thyroidea ima, is sometimes present; it arises from the arch of the aorta and enters the thyroid in the midline.
A venous plexus forms under the thyroid capsule. Each lobe is drained by the superior thyroid vein at the upper pole and the middle thyroid vein at the middle part of the lobe, both of which enter the internal jugular vein. Arising from each lower pole are the inferior thyroid veins, which drain directly into the innominate vein.
Thyroid Innervation
Significantly, the thyroid gland receives innervation from both the sympathetic and parasympathetic divisions of the autonomic nervous system. The sympathetic fibers arise from the cervical ganglia and enter with blood vessels, whereas the parasympathetic fibers are derived from the vagus and reach the gland via branches of the laryngeal nerves. The thyroid gland""s relation to the recurrent laryngeal nerves and to the external branch of the superior laryngeal nerves is of major surgical significance, since damage to these nerves can lead to a disability of phonation.
Sympathetic innervation of the thyroid cells has been reported to exert a stimulatory effect upon thyroid hormone release through adrenergic receptors for norepinephrine on follicle cells. Endocrinology 1979;105:7-9. Significantly, the human thyroid is also innervated by cholinergic, parasympathetic fibers. Cell Tiss Res 1978;195:367-370. See also Biol Signals 1994;3:15-25. And other mammalian species are known to also have cholinergicly innervated thyroid cells. See e.g. Z. Mikrosk Anat Forsch Leipzig 1986;100:1,S, 34-38 (pig thyroid is cholinergicly innervated); Neuroendocrinology 1991;53:69-74 (rat thyroid is cholinergicly innervated); Endocrinology 1984;114:1266-1271 (dog thyroid is cholinergicly innervated);
It has been reported that stimulation of the vagal nerve increases both thyroid blood flow and thyroid hormone secretion (Cell Tiss Res 1978;195:367-370), but this is apparently due to the extensive, generalized effect of vagal stimulation which can trigger a number of reflexes ascribed to the whole vagus territory. It is therefore inappropriate to conclude from this observation the vagal stimulation acts directly upon the thyroid to increase thyroid hormone release.
Significantly, the consensus is that cholinergic, parasympathetic influence upon thyroid hormone secretion by thyroid follicle cells, and presumably also of the intimately associated C cells, in inhibitory. Endocrinology 1979;105:7-9; Endocrinology 1984;114:1266-1271; Peptides 1985;6:585-589; Peptides 1987,8:893-897, and; Brazilian J Med Biol Res 1994;27:573-599. The direct cholinergic influence upon the thyroid appears to be mediated by muscarinic acetylcholine receptors of thyroid follicle cells since the cholinergic inhibition is blocked by atropine. Endocrinology 1979;105:7. The proximity of the non-follicular, calcitonin secreting cells of the thyroid to the thyroid hormone secreting follicle cells has led to the conclusion that parasympathetic influence over the C cells is also inhibitory.
Thyroid underactivity can be due to a dietary lack of iodine, the lack of which prevents thyroid cell synthesis of the thyroid hormones. In the Western world, Hashimoto""s disease is the most common cause of hypothyroidism. Hypothyroidism can also result from radio-iodine treatment or surgery to correct thyroid overactivity, as well as to a pituitary disorder.
The treatment of choice for hypothyroidism is replacement therapy with thyroxine. Treatment of hypothyroidism by thyroid hormone replacement requires long term, daily dosing with expensive medication from which undesirable side effects can occur. Problems with thyroxine therapy to treat hypothyroidism can include patient noncompliance, drug interactions, cardiac disease, bone density changes, lung disease and adrenal insufficiency. Braverman, L., et al, Diseases of the Thyroid, page 157, Humana Press (1997).
Clearly, there is a considerable need for an effective and suitable alternative to thyroid hormone replacement to treat the hypothyroidism of Hashimoto""s thyroiditis.
Botulinum Toxin
The anaerobic, gram positive bacterium Clostridium botulinum produces a potent polypeptide neurotoxin, botulinum toxin, which causes a neuroparalytic illness in humans and animals referred to as botulism. The spores of Clostridium botulinum are found in soil and can grow in improperly sterilized and sealed food containers of home based canneries, which are the cause of many of the cases of botulism. The effects of botulism typically appear 18 to 36 hours after eating the foodstuffs infected with a Clostridium botulinum culture or spores. The botulinum toxin can apparently pass unattenuated through the lining of the gut and attack peripheral motor neurons. Symptoms of botulinum toxin intoxication can progress from difficulty walking, swallowing, and speaking to paralysis of the respiratory muscles and death.
Botulinum toxin type A is the most lethal natural biological agent known to man. About 50 picograms of a commercially available botulinum toxin type A (purified neurotoxin complex)1 is a LD50 in mice (i.e. 1 unit). Interestingly, on a molar basis, botulinum toxin type A is about 1.8 billion times more lethal than diphtheria, about 600 million times more lethal than sodium cyanide, about 30 million times more lethal than cobra toxin and about 12 million times more lethal than cholera. Singh, Critical Aspects of Bacterial Protein Toxins, pages 63-84 (chapter 4) of Natural Toxins II, edited by B. R. Singh et al., Plenum Press, New York (1996) (where the stated LD50 of botulinum toxin type A of 0.3 ng equals 1 U is corrected for the fact that about 0.05 ng of BOTOX(copyright) equals 1 unit). One unit (U) of botulinum toxin is defined as the LD50 upon intraperitoneal injection into female Swiss Webster mice weighing 18 to 20 grams each.
Available from Allergan, Inc., of Irvine, Calif. under the tradename BOTOX(copyright) in 100 unit vials. One unit of BOTOX(copyright) contains about 50 picograms of botulinum toxin type A complex.
Seven immunologically distinct botulinum neurotoxins have been characterized, these being respectively botulinum neurotoxin serotypes A, B, C1, D, E, F and G each of which is distinguished by neutralization with type-specific antibodies. The different serotypes of botulinum toxin vary in the animal species that they affect and in the severity and duration of the paralysis they evoke. For example, it has been determined that botulinum toxin type A is 500 times more potent, as measured by the rate of paralysis produced in the rat, than is botulinum toxin type B. Additionally, botulinum toxin type B has been determined to be non-toxic in primates at a dose of 480 U/kg which is about 12 times the primate LD50 for botulinum toxin type A. Botulinum toxin apparently binds with high affinity to cholinergic motor neurons, is translocated into the neuron and blocks the release of acetylcholine.
Botulinum toxins have been used in clinical settings for the treatment of neuromuscular disorders characterized by hyperactive skeletal muscles. Botulinum toxin type A has been approved by the U.S. Food and Drug Administration for the treatment of blepharospasm, strabismus and hemifacial spasm. Non-type A botulinum toxin serotypes apparently have a lower potency and/or a shorter duration of activity as compared to botulinum toxin type A. Clinical effects of peripheral intramuscular botulinum toxin type A are usually seen within one week of injection. The typical duration of symptomatic relief from a single intramuscular injection of botulinum toxin type A averages about three months.
Although all the botulinum toxins serotypes apparently inhibit release of the neurotransmitter acetylcholine at the neuromuscular junction, they do so by affecting different neurosecretory proteins and/or cleaving these proteins at different sites. For example, botulinum types A and E both cleave the 25 kiloDalton (kD) synaptosomal associated protein (SNAP-25), but they target different amino acid sequences within this protein. Botulinum toxin types B, D, F and G act on vesicle-associated protein (VAMP, also called synaptobrevin), with each serotype cleaving the protein at a different site. Finally, botulinum toxin type C1 has been shown to cleave both syntaxin and SNAP-25. These differences in mechanism of action may affect the relative potency and/or duration of action of the various botulinum toxin serotypes. Significantly, it is known that the cytosol of pancreatic islet B cells contains at least SNAP-25 (Biochem J 1;339 (pt 1): 159-65 (April 1999)), and synaptobrevin (Mov Disord 1995 May; 10(3): 376).
The molecular weight of the botulinum toxin protein molecule, for all seven of the known botulinum toxin serotypes, is about 150 kD. Interestingly, the botulinum toxins are released by Clostridial bacterium as complexes comprising the 150 kD botulinum toxin protein molecule along with associated non-toxin proteins. Thus, the botulinum toxin type A complex can be produced by Clostridial bacterium as 900 kD, 500 kD and 300 kD forms. Botulinum toxin types B and C, is apparently produced as only a 500 kD complex. Botulinum toxin type D is produced as both 300 kD and 500 kD complexes. Finally, botulinum toxin types E and F are produced as only approximately 300 kD complexes. The complexes (i.e. molecular weight greater than about 150 kD) are believed to contain a non-toxin hemaglutinin protein and a non-toxin and non-toxic nonhemaglutinin protein. These two non-toxin proteins (which along with the botulinum toxin molecule comprise the relevant neurotoxin complex) may act to provide stability against denaturation to the botulinum toxin molecule and protection against digestive acids when toxin is ingested. Additionally, it is possible that the larger (greater than about 150 kD molecular weight) botulinum toxin complexes may result in a slower rate of diffusion of the botulinum toxin away from a site of intramuscular injection of a botulinum toxin complex.
In vitro studies have indicated that botulinum toxin inhibits potassium cation induced release of both acetylcholine and norepinephrine from primary cell cultures of brainstem tissue. Additionally, it has been reported that botulinum toxin inhibits the evoked release of both glycine and glutamate in primary cultures of spinal cord neurons and that in brain synaptosome preparations botulinum toxin inhibits the release of each of the neurotransmitters acetylcholine, dopamine, norepinephrine, CGRP and glutamate.
Botulinum toxin type A can be obtained by establishing and growing cultures of Clostridium botulinum in a fermenter and then harvesting and purifying the fermented mixture in accordance with known procedures. All the botulinum toxin serotypes are initially synthesized as inactive single chain proteins which must be cleaved or nicked by proteases to become neuroactive. The bacterial strains that make botulinum toxin serotypes A and G possess endogenous proteases and serotypes A and G can therefore be recovered from bacterial cultures in predominantly their active form. In contrast, botulinum toxin serotypes C1, D and E are synthesized by nonproteolytic strains and are therefore typically unactivated when recovered from culture. Serotypes B and F are produced by both proteolytic and nonproteolytic strains and therefore can be recovered in either the active or inactive form. However, even the proteolytic strains that produce, for example, the botulinum toxin type B serotype only cleave a portion of the toxin produced. The exact proportion of nicked to unnicked molecules depends on the length of incubation and the temperature of the culture. Therefore, a certain percentage of any preparation of, for example, the botulinum toxin type B toxin is likely to be inactive, possibly accounting for the known significantly lower potency of botulinum toxin type B as compared to botulinum toxin type A. The presence of inactive botulinum toxin molecules in a clinical preparation will contribute to the overall protein load of the preparation, which has been linked to increased antigenicity, without contributing to its clinical efficacy. Additionally, it is known that botulinum toxin type B has, upon intramuscular injection, a shorter duration of activity and is also less potent than botulinum toxin type A at the same dose level.
High quality crystalline botulinum toxin type A can be produced from the Hall A strain of Clostridium botulinum with characteristics of xe2x89xa73xc3x97107 U/mg, an A260/A278 of less than 0.60 and a distinct pattern of banding on gel electrophoresis. The known Schantz process can be used to obtain crystalline botulinum toxin type A, as set forth in Schantz, E. J., et al, Properties and use of Botulinum toxin and Other Microbial Neurotoxins in Medicine, Microbiol Rev. 56: 80-99 (1992). Generally, the botulinum toxin type A complex can be isolated and purified from an anaerobic fermentation by cultivating Clostridium botulinum type A in a suitable medium. The known process can also be used, upon separation out of the non-toxin proteins, to obtain pure botulinum toxins, such as for example: purified botulinum toxin type A with an approximately 150 kD molecular weight with a specific potency of 1-2xc3x97108 LD50 U/mg or greater; purified botulinum toxin type B with an approximately 156 kD molecular weight with a specific potency of 1-2xc3x97108 LD50 U/mg or greater, and; purified botulinum toxin type F with an approximately 155 kD molecular weight with a specific potency of 1-2xc3x97107 LD50 U/mg or greater.
Already prepared and purified botulinum toxins and toxin complexes can be obtained from List Biological Laboratories, Inc., Campbell, Calif.; the Centre for Applied Microbiology and Research, Porton Down, U.K.; Wako (Osaka, Japan), as well as from Sigma Chemicals of St Louis, Mo.
Pure botulinum toxin is so labile that it is generally not used to prepare a pharmaceutical composition. Furthermore. the botulinum toxin complexes, such the toxin type A complex are also extremely susceptible to denaturation due to surface denaturation, heat, and alkaline conditions. Inactivated toxin forms toxoid proteins which may be immunogenic. The resulting antibodies can render a patient refractory to toxin injection.
As with enzymes generally, the biological activities of the botulinum toxins (which are intracellular peptidases) is dependant, at least in part, upon their three dimensional conformation. Thus, botulinum toxin type A is detoxified by heat, various chemicals surface stretching and surface drying. Additionally, it is known that dilution of the toxin complex obtained by the known culturing, fermentation and purification to the much, much lower toxin concentrations used for pharmaceutical composition formulation results in rapid detoxification of the toxin unless a suitable stabilizing agent is present. Dilution of the toxin from milligram quantities to a solution containing nanograms per milliliter presents significant difficulties because of the rapid loss of specific toxicity upon such great dilution. Since the toxin may be used months or years after the toxin containing pharmaceutical composition is formulated, the toxin must be formulated with a stabilizing agent, such as albumin.
A commercially available botulinum toxin containing pharmaceutical composition is sold under the trademark BOTOX(copyright) (available from Allergan, Inc., of Irvine, Calif.). BOTOX(copyright) consists of a purified botulinum toxin type A complex, albumin and sodium chloride packaged in sterile, vacuum-dried form. The botulinum toxin type A is made from a culture of the Hall strain of Clostridium botulinum grown in a medium containing N-Z amine and yeast extract. The botulinum toxin type A complex is purified from the culture solution by a series of acid precipitations to a crystalline complex consisting of the active high molecular weight toxin protein and an associated hemagglutinin protein. The crystalline complex is re-dissolved in a solution containing saline and albumin and sterile filtered (0.2 microns) prior to vacuum-drying. BOTOX(copyright) can be reconstituted with sterile, non-preserved saline prior to intramuscular injection. Each vial of BOTOX(copyright) contains about 100 units (U) of Clostridium botulinum toxin type A purified neurotoxin complex, 0.5 milligrams of human serum albumin and 0.9 milligrams of sodium chloride in a sterile, vacuum-dried form without a preservative.
BOTOX(copyright) can be reconstituted with 0.9% Sodium Chloride Injection. Since BOTOX(copyright) can be denatured by bubbling or similar violent agitation, the diluent is gently injected into the vial. BOTOX(copyright) should be administered within four hours after reconstitution. During this time period, reconstituted BOTOX(copyright) is stored in a refrigerator (2xc2x0 to 8xc2x0 C.). Reconstituted BOTOX(copyright) is clear, colorless and free of particulate matter. The vacuum-dried product is stored in a freezer at or below xe2x88x925xc2x0 C. BOTOX(copyright) is administered within four hours after the vial is removed from the freezer and reconstituted. During these four hours, reconstituted BOTOX(copyright) can be stored in a refrigerator (2xc2x0 to 8xc2x0 C.). Reconstituted BOTOX(copyright) is clear, colorless and free of particulate matter.
It has been reported that botulinum toxin type A has been used in clinical settings as follows:
(1) about 75-125 units of BOTOX(copyright) per intramuscular injection (multiple muscles) to treat cervical dystonia;
(2) 5-10 units of BOTOX(copyright) per intramuscular injection to treat glabellar lines (brow furrows) (5 units injected intramuscularly into the procerus muscle and 10 units injected intramuscularly into each corrugator supercilii muscle);
(3) about 30-80 units of BOTOX(copyright) to treat constipation by intrasphincter injection of the puborectalis muscle;
(4) about 1-5 units per muscle of intramuscularly injected BOTOX(copyright) to treat blepharospasm by injecting the lateral pre-tarsal orbicularis oculi muscle of the upper lid and the lateral pre-tarsal orbicularis oculi of the lower lid.
(5) to treat strabismus, extraocular muscles have been injected intramuscularly with between about 1-5 units of BOTOX(copyright), the amount injected varying based upon both the size of the muscle to be injected and the extent of muscle paralysis desired (i.e. amount of diopter correction desired).
(6) to treat upper limb spasticity following stroke by intramuscular injections of BOTOX(copyright) into five different upper limb flexor muscles, as follows:
(a) flexor digitorum profundus: 7.5 U to 30 U
(b) flexor digitorum sublimus: 7.5 U to 30 U
(c) flexor carpi ulnaris: 10 U to 40 U
(d) flexor carpi radialis: 15 U to 60 U
(e) biceps brachii: 50 U to 200 U. Each of the five indicated muscles has been injected at the same treatment session, so that the patient receives from 90 U to 360 U of upper limb flexor muscle BOTOX(copyright) by intramuscular injection at each treatment session.
(7) to treat migraine, pericranial injected (injected symmetrically into glabellar, frontalis and temporalis muscles) injection of 25 U of BOTOX(copyright) has showed significant benefit as a prophylactic treatment of migraine compared to vehicle as measured by decreased measures of migraine frequency, maximal severity, associated vomiting and acute medication use over the three month period following the 25 U injection.
The success of botulinum toxin type A to treat a variety of clinical conditions has led to interest in other botulinum toxin serotypes. A study of two commercially available botulinum type A preparations (BOTOX(copyright) and Dysport(copyright)) and preparations of botulinum toxins type B and F (both obtained from Wako Chemicals, Japan) has been carried out to determine local muscle weakening efficacy, safety and antigenic potential. Botulinum toxin preparations were injected into the head of the right gastrocnemius muscle (0.5 to 200.0 units/kg) and muscle weakness was assessed using the mouse digit abduction scoring assay (DAS). ED50 values were calculated from dose response curves. Additional mice were given intramuscular injections to determine LD50 doses. The therapeutic index was calculated as LD5/ED50. Separate groups of mice received hind limb injections of BOTOX(copyright) (5.0 to 10.0 units/kg) or botulinum toxin type B (50.0 to 400.0 units/kg), and were tested for muscle weakness and increased water consumption, the later being a putative model for dry mouth. Antigenic potential was assessed by monthly intramuscular injections in rabbits (1.5 or 6.5 ng/kg for botulinum toxin type B or 0.15 ng/kg for BOTOX(copyright)). Peak muscle weakness and duration were dose related for all serotypes. DAS ED50 values (units/kg) were as follows: BOTOX(copyright): 6.7, Dysport(copyright): 24.7, botulinum toxin type B: 27.0 to 244.0, botulinum toxin type F: 4.3. BOTOX(copyright) had a longer duration of action than botulinum toxin type B or botulinum toxin type F. Therapeutic index values were as follows: BOTOX(copyright): 10.5, Dysport(copyright): 6.3, botulinum toxin type B: 3.2. Water consumption was greater in mice injected with botulinum toxin type B than with BOTOX(copyright), although botulinum toxin type B was less effective at weakening muscles. After four months of injections 2 of 4 (where treated with 1.5 ng/kg) and 4 of 4 (where treated with 6.5 ng/kg) rabbits developed antibodies against botulinum toxin type B. In a separate study, 0 of 9 BOTOX(copyright) treated rabbits demonstrated antibodies against botulinum toxin type A. DAS results indicate relative peak potencies of botulinum toxin type A being equal to botulinum toxin type F, and botulinum toxin type F being greater than botulinum toxin type B. With regard to duration of effect, botulinum toxin type A was greater than botulinum toxin type B, and botulinum toxin type B duration of effect was greater than botulinum toxin type F. As shown by the therapeutic index values, the two commercial preparations of botulinum toxin type A (BOTOX(copyright) and Dysport(copyright)) are different. The increased water consumption behavior observed following hind limb injection of botulinum toxin type B indicates that clinically significant amounts of this serotype entered the murine systemic circulation. The results also indicate that in order to achieve efficacy comparable to botulinum toxin type A, it is necessary to increase doses of the other serotypes examined. Increased dosage can comprise safety. Furthermore, in rabbits, type B was more antigenic than was BOTOX(copyright), possibly because of the higher protein load injected to achieve an effective dose of botulinum toxin type B. Eur J Neurol Nov. 6, 1999 (Supp 4):S3-S10.
Acetylcholine
Typically only a single type of small molecule neurotransmitter is released by each type of neuron in the mammalian nervous system. The neurotransmitter acetylcholine is secreted by neurons in many areas of the brain, but specifically by the large pyramidal cells of the motor cortex, by several different neurons in the basal ganglia, by the motor neurons that innervate the skeletal muscles, by the preganglionic neurons of the autonomic nervous system (both sympathetic and parasympathetic), by the postganglionic neurons of the parasympathetic nervous system, and by some of the postganglionic neurons of the sympathetic nervous system. Essentially, only the postganglionic sympathetic nerve fibers to the sweat glands, the piloerector muscles and a few blood vessels are cholinergic as most of the postganglionic neurons of the sympathetic nervous system secret the neurotransmitter norepinephine. In most instances acetylcholine has an excitatory effect. However, acetylcholine is known to have inhibitory effects at some of the peripheral parasympathetic nerve endings, such as inhibition of heart rate by the vagal nerve.
The efferent signals of the autonomic nervous system are transmitted to the body through either the sympathetic nervous system or the parasympathetic nervous system. The preganglionic neurons of the sympathetic nervous system extend from preganglionic sympathetic neuron cell bodies located in the intermediolateral horn of the spinal cord. The preganglionic sympathetic nerve fibers, extending from the cell body, synapse with postganglionic neurons located in either a paravertebral sympathetic ganglion or in a prevertebral ganglion. Since, the preganglionic neurons of both the sympathetic and parasympathetic nervous system are cholinergic, application of acetylcholine to the ganglia will excite both sympathetic and parasympathetic postganglionic neurons.
Acetylcholine activates two types of receptors, muscarinic and nicotinic receptors. The muscarinic receptors are found in all effector cells stimulated by the postganglionic neurons of the parasympathetic nervous system, as well as in those stimulated by the postganglionic cholinergic neurons of the sympathetic nervous system. The nicotinic receptors are found in the synapses between the preganglionic and postganglionic neurons of both the sympathetic and parasympathetic. The nicotinic receptors are also present in many membranes of skeletal muscle fibers at the neuromuscular junction.
Acetylcholine is released from cholinergic neurons when small, clear, intracellular vesicles fuse with the presynaptic neuronal cell membrane. A wide variety of non-neuronal secretory cells, such as, adrenal medulla (as well as the PC12 cell line) and pancreatic islet cells release catecholamines and thyroid hormone, respectively, from large dense-core vesicles. The PC12 cell line is a clone of rat pheochromocytoma cells extensively used as a tissue culture model for studies of sympathoadrenal development. Botulinum toxin inhibits the release of both types of compounds from both types of cells in vitro, permeabilized (as by electroporation) or by direct injection of the toxin into the denervated cell. Botulinum toxin is also known to block release of the neurotransmitter glutamate from cortical synaptosomes cell cultures.
What is needed therefore is an effective, long lasting, non-surgical resection, non-radiotherapy, non-systemic drug administration, therapeutic drug and method for treating Hashimoto""s thyroiditis.
The present invention meets this need and provides an effective, non-surgical resection, relatively long term, non-radiotherapy, non-systemic drug administration, therapeutic method for treating Hashimoto""s thyroiditis. The drug within the scope of this invention for treating Hashimoto""s thyroiditis is a neurotoxin.
As used herein xe2x80x9clocal administrationxe2x80x9d means direct injection of a neurotoxin into the thyroid. Systemic routes of administration, such as oral and intravenous routes of administration, are excluded from the scope of xe2x80x9clocal administrationxe2x80x9d of a neurotoxin.
As used herein, xe2x80x9cthyroid hormonexe2x80x9d means thyroxine (T4), while xe2x80x9cthyroid hormonesxe2x80x9d means triiodothyronine (T3) and thyroxine (T4).
A method for treating Hashimoto""s thyroiditis according to the present invention can be carried out by administration of a therapeutically effective amount of a neurotoxin to a patient, thereby treating Hashimoto""s thyroiditis.
A detailed method for treating Hashimoto""s thyroiditis according to the present invention can comprise the step of administration of a therapeutically effective amount of a botulinum toxin to a patient. Thus, a method for treating Hashimoto""s thyroiditis according to the present invention can comprise the step of local administration to the thyroid of a therapeutically effective amount of a botulinum toxin, thereby increasing a deficient thyroid hormone secretion from the thyroid cell and effectively treating the hypothyroidism of Hashimoto""s thyroiditis.
The neurotoxin can be administered in an amount of between about 10xe2x88x923 U/kg and about 35 U/kg. 35 U/kg is an upper limit because it approaches a lethal dose of certain neurotoxins, such as botulinum toxin type A. Other botulinum toxins, such as botulinum toxin type B, can be safely administered at several orders of magnitude higher dosage. Preferably, the neurotoxin is administered in an amount of between about 10xe2x88x922 U/kg and about 25 U/kg. More preferably, the neurotoxin is administered in an amount of between about 10xe2x88x921 U/kg and about 15 U/kg. Most preferably, the neurotoxin is administered in an amount of between about 1 U/kg and about 10 U/kg. In many instances, an administration of from about 1 units to about 500 units of a neurotoxin, such as a botulinum toxin type A, provides effective and long lasting therapeutic relief. More preferably, from about 5 units to about 300 units of a neurotoxin, such as a botulinum toxin type A, can be used and most preferably, from about 10 units to about 200 units of a neurotoxin, such as a botulinum toxin type A, can be locally administered into a target tissue such as the thyroid or a sympathetic ganglion with efficacious results. In a particularly preferred embodiment of the present invention from about 1 units to about 100 units of a botulinum toxin, such as botulinum toxin type A, can be locally administered into a target tissue such as the thyroid with therapeutically effective results.
The neurotoxin can be made by a Clostridial bacterium, such as by a Clostridium botulinum, Clostridium butyricum, Clostridium beratti or Clostridium tetani bacterium. Additionally, the neurotoxin can be a modified neurotoxin, that is a neurotoxin that has at least one of its amino acids deleted, modified or replaced, as compared to the native or wild type neurotoxin. Furthermore, the neurotoxin can be a recombinant produced neurotoxin or a derivative or fragment thereof.
The neurotoxin can be a botulinum toxin, such as one of the botulinum toxin serotypes A, B, C1, D, E, F or G. Preferably, the neurotoxin is botulinum toxin type A and the neurotoxin is locally administered by direct injection of the neurotoxin into the thyroid.
A detailed embodiment of a method within the scope of the present invention for treating Hashimoto""s thyroiditis can comprise the step of injecting a therapeutically effective amount of a botulinum toxin into a thyroid of a human patient, thereby increasing a thyroid hormone secretion from a thyroid cell and treating Hashimoto""s thyroiditis.
Another detailed embodiment of a method within the scope of the present invention for treating Hashimoto""s thyroiditis of a human patient can comprise the step of local administration to a cholinergic influenced thyroid cell of a human patient of a therapeutically effective amount of botulinum toxin type A, thereby increasing a cholinergic influenced deficient thyroid hormone secretion from the thyroid cell and treating Hashimoto""s thyroiditis.
A detailed embodiment of the present invention is a method for treating Hashimoto""s thyroiditis by injecting a therapeutically effective amount of a botulinum toxin into a thyroid of a human patient, thereby increasing a secretion of a thyroid hormone from a thyroid cell and treating Hashimoto""s thyroiditis. Preferably, the secretion treated is a cholinergic influenced secretion and the botulinum toxin used is botulinum toxin type A, although the botulinum toxin can selected from the group consisting of botulinum toxin types A, B, C (i.e. C1), D, E, F and G.
Significantly, the botulinum toxin can be is administered to the thyroid gland of the patient by placement of a botulinum toxin implant on or in the thyroid gland. The botulinum toxin is administered to the thyroid gland of the patient in an amount of between about 1 unit and about 10,000 units. When the botulinum toxin is botulinum toxin type A and the botulinum toxin administered to the thyroid gland of the patient in an amount of between about 1 unit and about 100 units.
Our invention encompasses a method for treating Hashimoto""s thyroiditis, the method comprising the step of administration of a therapeutically effective mount of botulinum toxin type A to the thyroid of a patient, thereby treating a symptom of Hashimoto""s thyroiditis.
The present invention is based upon the discovery that Hashimoto""s thyroiditis can be treated by in vivo administration of a neurotoxin to a patient. Thus, administration of a neurotoxin to the thyroid of a patient can remove an inhibitory cholinergic effect upon thyroid hormone secretion, thereby providing an effective treatment for the hypothyroidism of Hashimoto""s thyroiditis.
We have discovered that a particular neurotoxin, botulinum toxin, can be used with dramatic ameliorative effect to treat Hashimoto""s thyroiditis, thereby significantly superseding thereby current therapeutic regimens, such as oral thyroid hormone to treat hypothyroidism. Significantly, a single local administration of a neurotoxin, such as a botulinum toxin to the thyroid, according to the present invention, can increase thyroid hormone secretion and thereby treat symptoms of the hypothyroidism of Hashimoto""s thyroiditis. The symptoms of Hashimoto""s thyroiditis can be alleviated for at least about from 2 months to about 6 months per neurotoxin administration. Notably, it has been reported that glandular tissue treated by a botulinum toxin can show a reduced secretory activity for as long as 27 months post injection of the toxin. Laryngoscope 1999; 109:1344-1346, Laryngoscope 1998;108:381-384.
The Hashimoto""s thyroiditis hypothyroidism treatable by the present invention is hypothyroidism which has as a causative factor the inhibitory activity upon thyroid hormone secretion of parasympathetic innervation of the thyroid. Thus, treatment of Hashimoto""s thyroiditis hypothyroidism which results directly and solely from, for example, a dietary iodine deficiency or from the action of anti-thyroid antibodies, is outside the scope of the present invention. Notably, hypothyroidism resulting from a combination of factors, including inhibitory parasympathetic activity, is treatable by a method within the scope of the present invention.
A preferred embodiment of the present invention to treat Hashimoto""s thyroiditis is to inject the thyroid of a patient with from 1 to 500 units, more preferably from 5 to 200 units, and most preferably from 10 to 100 units of a neurotoxin (such as a botulinum toxin type A), to thereby cause an increase of thyroid follicle hormone secretion.
A neurotoxin, such as a botulinum toxin, locally administered in vivo to the thyroid to thereby remove an inhibitory effect upon a secretory activity of a thyroid follicle cell. Cholinergically innervated thyroid cells can be treated by is local administration of a neurotoxin, such as a botulinum toxin. By local administration it is meant that the neurotoxin is administered directly to or to the immediate vicinity of the thyroid tissue to be treated.
The specific dosage appropriate for administration is readily determined by one of ordinary skill in the art according to the factor discussed above. The dosage can also depend upon the size of the thyroid tissue mass to be treated or denervated, and the commercial preparation of the toxin. Additionally, the estimates for appropriate dosages in humans can be extrapolated from determinations of the amounts of botulinum required for effective denervation of other tissues. Thus, the amount of botulinum A to be injected is proportional to the mass and level of activity of the thyroid tissue to be treated. Generally, between about 0.01 and 35 units per kg of patient weight of a botulinum toxin, such as botulinum toxin type A, can be administered to effectively accomplish a toxin induced thyroid tissue secretion up regulation upon administration of the neurotoxin into the thyroid. Less than about 0.01 U/kg of a botulinum toxin does not have a significant therapeutic effect upon the secretory activity of a thyroid cell, while more than about 35 U/kg of a botulinum toxin approaches a toxic dose the neurotoxin. Careful placement of the injection needle and a low volume of neurotoxin used prevents significant amounts of botulinum toxin from appearing systemically. A more preferred dose range is from about 0.01 U/kg to about 25 U/kg of a botulinum toxin, such as that formulated as BOTOX(copyright). The actual amount of U/kg of a botulinum toxin to be administered depends upon factors such as the extent (mass) and level of activity of the thyroid tissue to be treated and the administration route chosen. Botulinum toxin type A is a preferred botulinum toxin serotype for use in the methods of the present invention.
Preferably, a neurotoxin used to practice a method within the scope of the present invention is a botulinum toxin, such as one of the serotype A, B, C, D, E, F or G botulinum toxins. Preferably, the botulinum toxin used is botulinum toxin type A, because of its high potency in humans, ready availability, and known safe and efficacious use for the treatment of skeletal muscle and smooth muscle disorders when locally administered by intramuscular injection.
The present invention includes within its scope the use of any neurotoxin which has a long duration therapeutic effect when locally applied to treat a Hashimoto""s thyroiditis. For example, neurotoxins made by any of the species of the toxin producing Clostridium bacteria, such as Clostridium botulinum, Clostridium butyricum, and Clostridium beratti can be used or adapted for use in the methods of the present invention. Additionally, all of the botulinum serotypes A, B, C, D, E, F and G can be advantageously used in the practice of the present invention, although type A is the most preferred serotype, as explained above. Practice of the present invention can provide effective relief of a thyroid disorder for from 2-27 months or longer in humans.
The present invention includes within its scope: (a) neurotoxin complex as well as pure neurotoxin obtained or processed by bacterial culturing, toxin extraction, concentration, preservation, freeze drying and/or reconstitution and; (b) modified or recombinant neurotoxin, that is neurotoxin that has had one or more amino acids or amino acid sequences deliberately deleted, modified or replaced by known chemical/biochemical amino acid modification procedures or by use of known host cell/recombinant vector recombinant technologies, as well as derivatives or fragments of neurotoxins so made, and includes neurotoxins with one or more attached targeting moieties for a cell surface receptor present on a thyroid cell.
Botulinum toxins for use according to the present invention can be stored in lyophilized or vacuum dried form in containers under vacuum pressure. Prior to lyophilization the botulinum toxin can be combined with pharmaceutically acceptable excipients, stabilizers and/or carriers, such as albumin. The lyophilized or vacuum dried material can be reconstituted with saline or water.
The route of administration and amount of a neurotoxin (such as a botulinum toxin serotype A, B, C, D, E, F or G) administered according to the present invention for treating a thyroid disorder can vary widely according to various patient variables including size, weight, age, disease severity, responsiveness to therapy, and solubility and diffusion characteristics of the neurotoxin toxin chosen. Furthermore, the extent of the thyroid or ganglionic tissue influenced is believed to be proportional to the volume of neurotoxin injected, while the quantity of the denervation is, for most dose ranges, believed to be proportional to the concentration of neurotoxin injected.
Our invention also includes within its scope the use of an implanted sustained release neurotoxin complex so as to provide therapeutic relief from a chronic thyroid disorder such as Hashimoto""s thyroiditis. Thus, the neurotoxin can be imbedded within, absorbed, or carried by a suitable polymer matrix which can be implanted or embedded in or on the thyroid gland so as to provide a year or more of delayed and controlled release of the neurotoxin to the desired target tissue. Implantable polymers which permit sustained, delayed release of polypeptide drugs are known, and can be used to prepare a botulinum toxin implant suitable for insertion or attachment onto or within the thyroid gland. See e.g. Pain 1999;82(1):49-55; Biomaterials 1994;15(5):383-9; Brain Res 1990;515(1-2):309-11 and U.S. Pat. Nos. 6,022,554; 6,011,011; 6,007,843; 5,667,808, and; 5,980,945.
Methods for determining the appropriate route of administration and dosage are generally determined on a case by case basis by the attending physician. Such determinations are routine to one of ordinary skill in the art (see for example, Harrison""s Principles of Internal Medicine (1998), edited by Anthony Fauci et al., 14th edition, published by McGraw Hill). For example, to treat a thyroid disorder, a solution of botulinum toxin type A complex can be endoscopically or intraperitoneally injected directly into the tissues of the thyroid, thereby substantially avoiding entry of the toxin into the systemic circulation.